Wireless receiving circuit



Dec. 26, 1933. N. P. HINTON 1,941,305

WIRELESS RECEIVING 'CIRCUIT Filed May 4, 1933 4- S/G/VALS w I 5 2 JK fli 1 06756702 7 kg 2 2Q 4QQ4L QSQLLATOQ INVENTOR BY Wig/Q ATTORNEY Patented Dec. 26, 1933 1,941,305 mEL s EQE V'I G Q R' v Norman Pullen Hinton, London, England Application May 4, 1933,. Serial No. 669,806, and 'I inGreat Britain November 1'7, 1931 1 Claim.

This. invention relates to tunable resonant cirl m ments an has in abje t; e d. izrr q were ii u i ar n men u tabl e 1158. W wi s. #9 1 exam l a w e eisr se r u h ot l m ted; o. t a pliwion esis the lYQi iQP is ear icular rwe u d w pr r qe'ai eeble rcu t arr n men i h 1 e sqnir l sd r m. a n e o r a d e n ich e ete iq i e wha ma be a me was as 'f e eqns a t r t c- T139 is t en, mana eu d. o. roe r2.i-,. of 5 rd nar e ir siiee and a an m n m be associated together in a comple g circuit arrangeinent having band pass characteristics.

the. invention may be. utilized to associate a local oscillator-circuit wlth'a high frequency receivmg circuit in such manner as to; provide a con:

stant frequency diiterence (equal to the beat freqeri y of; the receiver) throughout thtuning.

range h r ei er as a .wh le- From s roadest aspect the invention proca ities. continuous adjustment throughout a tuning a e an a in in eac 9si i0n a 1 t:

mi i w ut a ran e e n que es W a se t m 3 ;one another by a prede 'ned frequency dif i c which meaty: rrcien rem i s 5gb".

stantially constant (though the difference may be adjustable if desired) as the circuit arrangement is adjusted" over its said'range. The ins vention may be regarded as providinga complex Ani po tant ct l featureoi the inven-.

tion, lies} therefore, in the, provision of the 4 coupling unit as a selficontainedunit which may be manufactured andsold separately and. which a be utilized to connect together two: simple acceptor circuits having; similar. tuning reactances (tuning condensers) of any of the normal standardized types adapted fongang control.

The acceptor circuits'may .be's'eparately screened to prevent mutualinductance'therebetween, and

the coupling unit may be similarly screened.

Where the said unit i-smahufactured for sepascreened unit having. external terminals;

. The mainieature of the. invention resides .in'

the vassociation together ,of two slang controlled uned c rcu s-by m ans 31 i a oupling circuit; e d; u ed. c rcui inconiuncti nz "with, addedunit whereby two tuned circuits A far he app i ation. c t e nv ie is t u e meyn e eiv n ic pl ation.

a omel em e e s m nt ab e Q two diifer ent rate sale; it is preferablyzin the form. of a reactance provided by the coupling circuit constituting a complex circuit tunable by operation of al'sin gle handle and having for each position of tuning'at' least two resonant anodes 'of oscillation at two, different freq'uenciea'the whole arrangementbeing such that mutual inductance between the said tuned circuits is. avoided, the required; constancy of frequency difierence beingv obtained, without such mutualinductance and. solely by virtue of'the self-inductance and capacities of the reactance elements employed. This. results in the important, practical advantage that accurate calculation. and: design and manufacture from such design is a. comparatively simple matter; which, of course, is not the case in arrangements depending upon mutual inductance. effects which change; quantitatively with frequency.; I In carrying, the invention into, practice as. applied to; band pass tunable filter arrangements, such as are irequentlyrequired in radio rec'eiv.* ers; so 'asct'o tune said receivers to any desired. r dio transmitting station within the range there of, a constant width of frequency band (e. g. that corresponding to the modulation side bands necessary forgood quality musical reproduction) -may be arranged for; or, by making-the coupling circuit adjustable, an adjustment of the band width may be provided for. The invention is illustrated in the accompanying diagrammatic drawing in which: various arrangements in accordancetherewith are shown.

In d awin .Fig. 1 shows one embodiment of the invention, -Eigs. 2, 3, l respectively show, different modis aii ns of the. ar n emen of Fig. shows the application of, the arrangement oi Fig. 2'to asuperheterodyne receiver.

Beferringtqliig. 1 this showsa circuit arrangemer t; consisting of two equalvariable condensers K1 and K2; two equal'fixed inductances L1 and L2; two, equal fixed condensers R11 and J02; andtwo'iurther equal variable inductances a1 andaz. a Wil seenme nde ser K s connected at one end to the inductance L1, and the condenser K2 is similarly connected at one end to the in-.

ductance' L2. The remaining end of L2 is connected to the remaining endof K1 through the condenser k2, and the remaining end of.L1'is connected to the remaining end of K through the condenser. In.

The inductance a1 is connected between the ends of L1"a.nl'l"L2 remote from the condensers Krand K2, and the inductance a2 is connected betweenthe other sidesof the two condensers K1 K2. As. will be seen, at one particular irequency, namely that at. which K1 and (L1+ai) resonatewith one another (K2 will, of course, re's-. onate with (L2.+d2) at'. the same frequency), minimum potentials. will exist across the series tuned circuits (L1[(L1) and K1 and (L2+a2) and K2, and it is for this reason that the condensers in and 702 may be connectedacross the points indicated. 7 1

These condensers K1 K2 are the tuning con densers, and are adjusted together (ganged) for tuning. The inductances a1 112 are small rela tive to the main inductances L1 and L2. The whole circuit shown in Fig. 1 has two modes of oscillation, namely around the series loop consisting of K1 L1 or L2 K2 a2, and, also, in a figure of eight circuit through Ki L1 701 K2 L2 k2 back to K1. The wave length for the first, or series, mode of oscillation will be proportional to:

while for the parallel, or figure of eight, mode of oscillation the wave length will be proportional to:

In Fig. 1 the coupling circuit consists of the numbers a1 d2 k1 702, and this circuit may be manufactured and sold separately as a self-contained screenedunit having four external terminals.

Fig. 2 shows a slight modification of the arrangement shown in Fig. l, the modification consisting in changing the positions of those inductances and condensers indicated-by small reference letters. In the case of Fig. 2, the Wave length obtained for the series mode of oscillation will be proportional to the quantity (2), above given for the wave length obtained for the figure of eight mode of oscillation in Fig. 1, while the wave length obtained for the figure of eight-mode of tancesmay be similarly tapped and arranged to be adjustable from a common handle.

Fig. 3 shows a further modification to which neither additional induotances nor additional condensers are included in the circuit through which i the series mode of oscillation occurs, but instead two circuits, each consistlngof an inductance a'i in series'with a condenser /1 or a2 in series with a condenser lc'2, are connected diagonally across the said series circuit as shown in the said Fig. 3.

The circuit of Fig. 3 will again have two modes;

of oscillation, one, the series mode through K1 L1 L2 and K2, and the other the parallel or figure of eight mode through Ki W2 W2 K2 ai k1. In the series mode thewave length will be proportional to:

JEE=VL2K2 (3) while in the figure of eight mode, the wave length will be proportional to:

In Fig. 3, Li=L2', and K1=K2 as before, while ly smaller than L1 the difference in magnitude between these inductancesbeing determined by the frequency difierence required between the. frequencies obtained at the two modes of oscillation.;-The coupling circuit is, therefore, not so advantageous as are the coupling circuits of Figs}. 1 and 2 from the point of view of general use as a unitfor separate sale, since in Fig. 3 ai'a'nd a'z' are'co-relatedin value (for a given band width) withLi and L2, whereas in Figs. 1 and 2, a1 and a2 determine the band width irrespective of L1 and L2. i

Throughout Figs. 1 to 3 no mutual inductance exists between any two inductances. It is possible, however, in carrying out the invention to magnetically couple together the inductances additional to the main inductances, provided that the resultant inductance is equal to the separate additional inductances as set forth above, i. e. what may be termed the calculated additional inductances. The additional inductances may in practice be mounted in the same housingorf screening box employed for the maininductances,

provided that either, or both, are wound'astatically and. so arranged that substantially 'no volt-' tage is induced from oneinto the other.

Fig. 4 shows a still further modification wherein a series loop circuit consisting of a condenser K1; a main inductance L1, an added small inductance a1, a'second addedsmall inductance a2, a main inductance L2 and a condenser Kz 'is provided, the circuit being symmetrically bridged across by a series circuit consisting of two further spectivelyfand a condenser 101, the added inductances /2a1 a2 being equal each to half the magnitude of m or a2. Theinductance 'a'2 is very tightly coupled to the inductance 6123/1101 the inductance a1 is also very tightly coupled to the inductance a1. As will be seen themductances /zal and a2 will carry twice the cur small inductances designated a2 and /20t1 rea mode, and, therefore, for this mode of oscillation J the effects produced by the inductances a1 and a cancel out, while in the series mode of oscillation equal and oppositeelectromotive forces will be induced in the inductances' ai A 'a and no voltage is produced'across the bridge for the series mode of oscillation. For Fig. 4 thewave length of the series mode of oscillation will be proportional to:

. 1( 1+ I).= 2( 2+F 2) (5) while in the bridge mode the wave length will be proportional tor K2]; fT I 1. K t 2 Fig. 5- showsthe arrangement of Fig. 2*employed'for a superheterodyne receiverthecircuit shown in Fig. 5 serving tohave' always two 'frequencies separated by a predeterminedfconstant difference equal to the m and a2, and the received signal carrier to the leads R C. The couplings should, of course, be such that the ends of the whole circuit arrangement are of like potential as regards local oscillator energy so that re-radiation is avoided;

desired beat frequency. The local oscillator energyis applied to the coilsintermediate frequency. This. circuit of Fig. 5

contains a tunable oscillator acceptor circuitjand a'tunabl'e pick-up circuitlor incoming signal,

with little or practically balanced oscillator signal back to the input aerial.

Having now particularly described and ascerand a tuning condenser in series, like ends of said acceptor circuits being coupled to one another bycondensers which are in series in a loop circuit with the two main inductances and the two tuning condensers, and opposite ends of said acceptor circuits being connected to one another through coupling inductances which are in series I in a figure of'eight circuit with the said two main inductances and the said tuning condensers, the two said main inductances having substantially no mutual inductance with one another.

- r NORMAN PULLEN HINTON. 

